rfiYsica. 595 



termining the exact number of vibrations made per second by means of 

 a spark produced between the tuning-fork style and the metal cylinder 

 whenever contact is established in an electrical circuit by means of a sec- 

 onds pendulum. This pendulum is provided with a triangular platinum 

 point, which as it vibrates cuts a small and rigid mercury globule on an 

 adjustable iron cup. The pendulum and mercury globule are in the 

 primary circuit of an inductorium, the fork and cylinder in the second- 

 ary circuit. It is essential that the discharge should not be multiple, 

 but should consist of only a single spark, a result secured by varying the 

 strength of the current in the primary circuit and the size of the con- 

 denser in the secondary. The author used this method not only to deter- 

 mine the absolute pitch of tuning forks, but also to determine the abso- 

 lute constancy of the pitch with decreasing amplitude, and, in conjunc- 

 tion with the method of beats, to study the effect of temperature on 

 pitch. He concludes that a Koenig fork gains or loses 2T5-^i- part of 

 a vibratory period by a change of temperature of 1° F. The effect of 

 the scrape of the style on the vibration of the fork was also measured 

 and found to be —'026 vibration. The results of his determinations of 

 the pitch of five European forks of various standards are given in the 

 memoir, and also some results of the use of the above method as a chro- 

 noscope. (Mem. Nat. Acad. Sci., 1885, iii, 45.) 



Ellis has given an account of the method of Mayer, and has compared 

 the results obtained by it with those of other methods, especially those 

 of Scheibler, of MacLeod, and of Koenig. The five forks sent to Mayer 

 had been measured by himself with Scheibler's tonometer, and also by 

 MacLeod. The results agreed within 0.1 vibration. Although Mayer 

 gives his results to three decimal places, Ellis thinks that the number 

 of varying circumstances is so great that " at most two jilaces of deci- 

 mals (perhaps only one) out of the three of Mayer's means can be trusted." 

 Hence he doubts whether Mayer's process is superior to Scheibler's, al- 

 though he concedes that it is fully equal to it. As a chronoscope, he 

 regards it as extremely valuable, since if the time of vibration be deter- 

 mined to Yoo of a vibration, and the fork makes 400 vibrations per sec- 

 ond, the measurement would be correct to -j-ooo^ ]^art of a second. As 

 to the effect of temperature, MacLeod finds the coefficient to be 204 9 o? 

 Koenig j-g^i^, and himself y^^Toj while Mayer, as above stated, ob- 

 tained the value 2T5 eT • {Nature, November, 1885, xxxiii, 54.) 



Soret has advocated the A of 432 vibrations as the standard of mu- 

 sical pitch. Objection seems to be raised to this suggestion, long ago 

 made in Belgium and rejected by a commission, who adopted in March, 

 1885, the French A of 435 vibrations. The arguments in favor of 432 

 are almost entirely arithmetical. But even if practicable to make a 

 fork exact in the arithmetical series at the start, the charm of the arith- 

 metic vanishes with a slight change in temperature. Up to 1813 all 

 Europe had used a pitch within a comma either way of Handel's fork 

 A 422-5. Then the Russian Emperor gave a set of new instruments t(j 



